In a semiconductor device, a power semiconductor element suitable for high voltage and large current applications is provided in a case, and a main terminal electrically connected to an electrode of the semiconductor element through a circuit pattern formed on a substrate and a wiring member such as a lead frame is provided on the outside of the case to make a package. The main terminal of the semiconductor device is connected to an external electric circuit. The semiconductor device mounted on equipment controls the operation of the equipment by controlling current flowing through the external electric circuit. Semiconductor devices are readily mounted on equipment and thus used in a wide variety of fields ranging from industrial equipment to home appliances.
A semiconductor element in a semiconductor device has a vertical structure having a front electrode and a back electrode, in which high voltage is applied between the front electrode and the back electrode and large current flows. In a semiconductor device, the back electrode of the semiconductor element is joined to an insulating substrate of a ceramic material with high thermal conductivity so that heat generated by the semiconductor element is efficiently dissipated. The electrical resistance of wiring connected to the front electrode of the semiconductor element is reduced by joining an electrode plate such as lead frame directly to the front electrode of semiconductor element with solder. The electrode plate has an area larger than the front electrode of the semiconductor element and is joined to the front electrode(s) of one or more semiconductor elements in the semiconductor device. The electrode plate is formed of a metal with high electrical conductivity, such as copper and aluminum. When the electrode plate is formed of aluminum, the surface of the electrode plate is metallized, for example, plated with copper to allow solder to wet.
In a conventional semiconductor device, the electrode plate has a half cut portion protruding from the surface of the electrode plate and an embossed portion further protruding from the half cut portion. The half cut portion on the protruding side is joined to the front electrode of the semiconductor element with solder. The embossed portion is brought into abutment and joined to the front electrode of the semiconductor element with solder, so that the amount of solder with the same thickness as the height of the embossed portion is kept between the front electrode of semiconductor element and the half cut portion of the electrode plate (for example, see PTL 1).